I like the idea of this application: let’s say you have an appointment and for some reason you are going to be late; you will have to notify people of this.

Sorry I’m Late is a free application for Windows Phones that uses cell tower info to find your (approximate) location and, with a nice Sense-like user interface, allows you to select recipients (quote: call history access to guess the most probable recipients) and notify them of your whereabouts and your estimated time of arrival. .NET Compact Framework 3.5 is required to run this app.